TRAGIC++ (interactive forest stand simulation program)

I know this may seem like a lot of focus on tree stuff, but canopy effects (such as interception) can be mighty important in HHWQ modeiling/simulation.

In TRAGIC++, the development of a forest is simulated as the collective dynamics of individually growing trees, each of which competes with the others for light, space and nutrients. Interaction is possible by removing or planting single or groups of trees and by changing the environmental conditions (light an nutrients).

http://www.bayceer.uni-bayreuth.de/mod/html/webapps/tragic++/index_englisch.html